Inkjet printers typically include one or a plurality of inkjet print heads, each including an array of nozzles formed on a nozzle face. The nozzles eject ink drops, the ink being provided from an ink supply through an ink path. Ink drop ejection may be controlled by suitable actuators such as piezoelectric transducers. In so-called “drop-on-demand” inkjet printers, each actuator may be selectively fired to eject a drop at a specific location on a substrate. The print heads and the substrate may be moved relatively to each other during the printing operation.
For high throughput, many inkjet printers comprise a plurality of inkjet print heads. Each print head is part of an inkjet print module. In addition to the print head, such a module features further components for the feeding and conditioning of ink, for controlling the ejection of the ink by the print head and/or for mechanical or thermical purposes. A plurality of such modules are mounted to a mounting assembly, in an adjoining relationship along a longitudinal direction of the mounting assembly, i. e. a so-called “print bar” is created. The nozzle arrays of adjacent print heads are arranged in such a way that seamless printing over the width of a plurality of inkjet print heads is possible. For that purpose, it is important to precisely position the adjacent inkjet print heads on the mounting assembly.
As an example, WO 2009/142927 A1 (Fujifilm Corporation) describes an adjustable print head mounting assembly comprising a frame, a fixed component configured to affix to the frame and a movable component adapted to move relative to the fixed component and the frame. The assembly comprises a first adjustment mechanism and a second adjustment mechanism, being configured to be operated individually to rotate the first or second end of the movable component, respectively, and to be operated together to translate the movable component in an angular direction relative to the frame. The adjustment mechanisms comprise adjustment screws that are accessible from the backside of the mounting assembly. The assembly may further comprise a motor connected to at least one of the first adjustment mechanism and the second adjustment mechanism, e. g. by reduction gears. In order to allow for seamless printing, the nozzle arrays are rhomboid shaped and the arrays of two adjoining print heads are slightly offset to each other in a direction perpendicular to the longitudinal direction.
Similarly, U.S. Pat. No. 8,297,736 B2 (FFEI Limited) relates to an assembly with a plurality of inkjet heads mounted thereon. The heads are mounted to a plurality of spaced apart carrier members mounted for relative movement along an elongate path. Each carrier includes laterally offset first and second coupling positions whereby in use alternate inkjet heads are coupled at each of their ends between first coupling positions or between second coupling positions, respectively, of successive pairs of carrier members. At least one coupling position of each carrier member includes an adjustment mechanism to enable parts of inkjet heads coupled to the respective coupling positions to be relatively aligned in the elongate direction.
Using the prior art mechanisms, manually adjusting the position of a plurality of inkjet print heads in order to allow for seamless printing is cumbersome. Providing each of the adjustment mechanisms with motor drives leads to substantially increased complexity, cost and weight of the inkjet printing assembly.